The primary aim of my PhD thesis was to identify and characterise novel modulators of intracellular signalling during early vertebrate development. The first phase of my thesis was to design and execute a large-scale gain of function screen in order to identify novel modulators of various important signal transduction pathways during early Xenopus development. From this screen I identified twenty novel of growth factor signalling. In the second phase of my PhD study, I concentrated on the characterization and mode of action of one of the genes I identified in the screen; namely fezf2. I showed that Fezf2 regulates neurogenesis in the diencephalon by locally promoting Wnt signalling through repression of lhx2 and lhx9. Notably, this investigation on the function of fezf2 not only revealed the previously undiscovered role of fezf2-mediated Wnt regulatory mechanism during diencephalon development, but also confirmed our in vivo screening approach in identifying potential regulators of signalling pathways. To the end, my PhD project has provided me with a fruitful journey of discovery, which started with the design and execution of a large-scale screen, ending with the detailed characterization of a factor involved in the modulation of signalling and forebrain development. This study is has broadened our understanding of how intracellular and extracellular signals are integrated during embryonic development process, which forms an interactive network ultimately resulting in appropriate cell differentiation, organ formation, and regional patterning.